Fluoromethylpyridines



Patented July 25, 1950 fu-'N1 T1: D sfrnres osFl-u 2516.402 I EUoRoME-THYLPYRIMNES NEarl T. McBee and Ernest M.2Hodnctt,.l;a Fayette, Ind., assignoi-stoTurduaReseanch Boundation, Tt/Vest Lafayette, Ind., a corporationoflndiana NoDrawing. Anplicationseptember 4,1945, SerialN0. 614,436

This inventionv relates to "certain (tr'il'luoromethyl) pyridines an'dis more particularly `concerned 'with'th'e 'compounds having one orttwo triflrucrornethyl' radicals attached to carbon yatoms of the pyridinering 'and which may orem'ay'not be further halogenatei onthe' ring.

' These compounds s are stable, water-White liquids or solids, insolublein water'andinconcentrated hydrochloric acid, and soluble '-i-nvarious organic solvents. 'In general, "they Vexhibit yno basic properties. "These compounds dare Vuseful -a-s intermediates in -the prepara-tion Aof other chemical compounds. -Theyhave been isolated in a state of a'nalytica-lpurityand the physical properties have'beendeterm-ined.

We have prepared V'these compounds *by the chlorination of methylpyridines,'=in tWliic'hfcomplete substitution took place on the side-chain and, in some cases, to some vextentfon'the-ring as well, the chlorine in the Aside-chains @being replaced subsequentlyby iiuorine. The chlorina tion of the side-chains may be carried out-at moderately elevated temperatures in Athe vpresence of actinic light. Chlorination on 'the pyri- -dirneri-nfg, :which is-.ordinarily difficult to accomplish, appears to .be aided in thisvcase by the .presence of one or more trichloromethyl groups on .the ring, .and r.goes .forward when'fthe teme peratures of the chlorination reaction are raised to about 200 centigrade. This iluorination may be accomplished with hydrogen fluoride.

The following examples'illustrate the practice of our invention but are not to .be construed `as limiting:

Example 1 Two hundred seventy-nine lgrams (3 moles) Aof 2-Inethylpyridine was .chlorinated in an electrically-heated, 4-foot length of Pyrex glass tubing., 5l y'milli-nleters in diameter. This Was fitted with a lthermo-rneter and acondenser, theexit of which led into` a -water trap. Chlorine ywas admitted through an eXtra-coarse gas dispersion disc. Light was supplied by -two banks of incandescent light bulbs.

Forty milliliters of water was added top the tube, covering the disc, theflowofchlorinewas started through the disc, and the 2methylpyridine was added. The temperature of the reaction mixture was maintained below 50 centigrade for two hours by iinmersing the tube in an ice-water bath. At this tin'lethere Was only one liquid layer. The ice was then allowed to melt and v-rolaims. (crest-2.90)

heat applied. yThe temperature was elevated to 115.0 Vnentigrade.during one hour andmaintained at thatpoin-t ton-about twenty-,nine hours.` The .rate oi Echlorine .flow was adjusted to .keep .the solution-saturated. -W-hen no more chlorine was .being absorbed, the .dow of .chlorine -yvasstopped andthe contents .oftheutube aerated. After. cooling, :the chlorinated productfand the hydrochloric .acid .form two .separate .layer-s. .The-lower ,layer .was .found to..oontainfiapercent .of chlorine. This flater .was .rectiiedat 15 .millimeters mercury pressure .absolute and ,several Lfractions were obtained. .Eromthese fractions theiollowing `.compounds were puried and .identiedz .-2-QtrichloromethyD pyridine ina vyield of 1.52 ,per .,cent, boiling at. 122 to v-.125 centigrade; 5-chloro-2- (.trichlbromethyl); pyridine, .ina yield of 9.7 per cent, boiling from 147 to 155 centi'- grade; 3,5-dichloro -f.2--'(- trichloromethyl) pyridine, .in a lyield of 16.9 per cent, boiling at 182 to i185 4centigrexle; and 34,5-trichioro.5i-(trich'loromethyl) pyridina'briiling at1'201@ to 205 centigrade. These compounds are insoluble `in Water andin concentratedhydrochloric `-acidbut soluble inorganic solvents. Y

"The chlorinated product-s Wer-e Htl-ien-lu n"i hated.' Five hundred 'tWentyH-four grams '(ap-A vproxinrrately :22/3 moles) -of `l2-('trichloromethyl) pyridine and-00 grams '(30 moles) `of hydrogen fluoride were placed Ain a one and 'one-'half 1liter nickel-lined autoclave and heated l-for' twentyeight hours ata Vmamimumtemgocrtaure G1-2O4 oentigrad-e. The produce, la bl'acklliquid conta-iin- -ing a considerable'quantityof hydrogen iiuoride, was steam-distilled, dri-ed with anhydrous I calcium chloride #and `vrectifiedl at reduced pressure on afi-.footglass-packed column. Several frac tions wer 'obtained' .comprising ringmchlorinated y'(triiiuoro-rnethyl) pyridines. Thus, 5-chloro-2- V(triiuorornetlrryl') .pyridinexina yieldbf i10.5 per cent, .boiling fat .85.5 :to `@91.0 at v100fmil1imeters of .pressure Y.absolute wasobtained. Onrecrystallization .the :coinpoundfmeltedat .37.5 toA 38.0 centigraderiand'boiled at .91 t-o:192fcentignade-at 100 millimeters pressure. 4The lmolecular;.weight of vthis compound wasi'iound `to be 181., correspondinrgtwrell tofthextheoretical molecular :weight :of echloro -2ez (triluoromethyl) pyridine." .Anald ysis showed .19.4 ."per:centzchlorinefand 29,6.;per cent fluorine, which corresponded substantially tovthe:theoreticalfvalues oi 119:5 andere perfcent respectively. Also, 1.315- dichioro-.:2 --(triuoro` methyl? ,pyridine was zobtainediboilingfatdimm-to 115 centigrade at 100 millimeters pressure and having a freezing point of centigrade. A density of 1.5122 and a refractive index of 1.4780 at centigrade.

Example 2 hours, and then raised to 180 centigrade for six hours. The product crystallized on standmg.

grams of crude 2,6-bis (trichloromethyl) pyridine which was recrystallized from 95 percent ethyl alcohol to give 237 grams or 37.8 per cent of puried product. The filtrate was later used inA This productwas then fluorinated in lized from 95 per cent ethyl alcohol to give 49.5

per cent of 2,6-bis-(triuoromethyl) pyridine, having a molecular weight of 215, melting at 56.5 to 57.5 centigrade, and boiling at 149 to 150 centigrade at 748 millimeters of mercury pressure absolute. The compound analyzed 52.4 per cent of fluorine, which corresponded well to the theoretical valuelof 53.2 per cent.

Example 3 The filtrate obtained by vacuumltration of the crystallized mixture ofv chlorinated 2,6-dimethylpyridine, comprising mostly 2,6bis(tri chloromethyl) pyridine, was further chlorinated to attain chlorination on the pyridine ring. Chio- Vacuum filtration of the product gave 128111, 5'

by heating in a one and one-half liter nickellined autoclave for twenty-nine and ve-tenths hours at a maximum temperature of 278 centigrade. The liquid product was steam-distilled. The steam-volatile product was dried and redistilled in an ordinary distilling flask. On rectication, we isolated from the product chloro- 2,6-bis (triuoromethyl) pyridine, boiling at 164.6 to 165 centigrade at 748.2 `millimeters ,pressuredreezing at 1.6 to 2.0 centigrade, and

having a density of 1.5644, and a refractive index of 1.4140 at 25 centigrade. The compound 'analyzed 14.1 per cent chlorine and 45.3 per cent uorine, corresponding substantially to the theoretical values of 14.2 and 45.8 per cent, respectively.

' Example 4 One hundred seven grams (1 mole) of 2,4-dlmethylpyridine was chlorinated in a manner similar to that outlined in Example 1 with some variation in temperature. The temperature of the reaction mixture was held below centigrade for three hours, raised to 150 centigrade during the next four hours, and maintained at that point for six hours. Water was added dropwise Yto prevent the precipitation of any hydrochloride during the chlorination. A crystalline product separated on cooling. This solid was recrystallized from 95 per cent ethyl alcohol, giving dark-colored crystals which we decolorized with activated charcoal. On a second recrystallization from dilute alcohol (200 milliliters of 95 per cent alcohol in 30 milliliters of water), White crystals were obtained having a melting point of 86.5 to 87.5 centigrade. This solid analyzed 67.8 per cent chlorine, which is the same as the theoretical value of chlorine in 2,4-bis (trichloromethyl) pyridine.

, `Fluorination of 2,4-bis (trichloromethyl) pyridine was accomplished by heating with hydrogen fluoride in a nickel-lined autoclave. The products, of' three uorinations were combined, steam distilled, dried, and reactified on a 50-inch Lecky-Ewell column. Several fractions were obtained. 2,4bis(trii1uoromethyl) pyridine, boiling at 69.5 to 70.5 centigrade at 100 millimeters presrine was added to thevmaterial in the presence of light in a glass reactor. The temperature was raised to 150 centigrade during the rst two hours, and was maintained at that ,temperature for fifteen and one-half hours. The temperature Y was then raised to 200 centigrade and maintained there for one and one-half hours. The chlorinated mixture, which `was a liquid at room temperature, was vacuum-distilledv and several fractions obtained, all of which crystallized on standing for a few hours. Some unreacted 2,6-bis- ""-3 (trichloromethyl) pyridine was obtained, but we alsov isolated a compound identified as chloro-2,6- bis(trichloromethyl) pyridine, boiling at 180, to

185 centigrade at 9 millimeters pressure absolute. Thisffraction' 'was recrystallized twice from 95 per cent ethyl alcohol and. a white solid Was obtained, melting at 86.5 to 87.5 centigrade, with a chlorine content of 71.6 per cent corresponding substantially to the theoretical value of 71.3 per cent. It is assumed that' the chlorine is subsure was obtained. 'This did not crystallize when cooled to -50centigrade. The density of this compound was 1.4701, and the refractive index was 1.3833 at 25 centigrade. It analyzed 51.4 per ,cent ilumine, the theoretical value for 11u0- rine being 53;.2 per cent. Chlor0-2,4bis (triuoromethyl)A pyridine, boiling at to 86 centigrade at millimeters pressure, was obtained which also did not crystallize when cooled to 50 centigrade. The density of this compound was 1.5426, andthe refractive index was 1.4113 at 25 centigra'de. This analyzed 13.0 per cent chlorine and 45.8 vper cent fluorine, corresponding substantially tothe theoretical values of 14.2 and 45.8, respectively. The yield of chloro-2,4-bis (trifluoromethyl) pyridine, based on 2,4-dimethylpyridine, was'10.5 per cent. It was assumed that the chlorine was substituted in the 5-position as substitution takes place most easily in the beta position in this compound.

Werclaim: y 'f 1'. `5chloro2(trifluoromethyl) pyridine having the'formula `CFa 5 2. 3,5 dichloro 2(triuoromethy1) pyridine 7. A fiuoromethylpyridine having the following having the formula structural formula:

5 (CF=). C1.. N CFs \N/ 3. 2,6-bis(truoromethy1) pyridine having the wherein m is an integer from one to two, inclusive, formula, and wherein n is an integer from zero to two, in-

x0 CluSVe.

EARL T. MCBEE. ERNEST M. I-IODNETT. CF CFS N REFERENCES CITED 4- 0111010216bis'tifuo'omethylpyrdne hav' 15 The following references are of record in the lng the formula file of this patent:

C1 UNITED STATES PATENTS Number Name Date 2o 2,121,330 Scherer June 21, 1938 0F=\N/OF' 2,180,772 Scherer Nov.21,1939

5. 2,4-bis(tri1iuoromethy1) pyridine having the FOREIGN PATENTS formula Number Country Date CF: o5 '786,123 France 1935 k OTHER REFERENCES Maier, Das Pyridine und Seine Derivatives" CF (1934) N 'l Chemical Abstracts, v01. 31 (1937), page 689. 6. Chloro 2,4 bis(triuoromethy1) pyridine 00 Groggins, Unit Processes in Organic Synthehaving the formula sis, 1938, pages 157 and 158.

CFS Sidgwick, Organic Chemistry of Nitrogen, Ox-

ford Press (1942). page 522 

7. A FLUOROMETHYLPYRIDINE HAVING THE FOLLOWING STRUCTURAL FORMULA: 